According to the Bureau of Meteorology, the storm formed at around midnight on the night of 2 December over Craigieburn, then grew in size as it moved in a south-easterly direction (the Bureau issued a severe thunderstorm warning based on their observations at 11.38pm).[1] The two hours from midnight to 2am saw extremely heavy rainfall, with some areas recording more than 100mm of rain in that time. The rapid rain fall caused flash flooding, which resulted in extensive damage to property.[2]